The present invention relates to combustion safety apparatus for preventing such danger as a lack of oxygen accident caused by incomplete combustion or unburned gas discharge caused by fire extinguishing.
With respect to apparatus of this kind, there has been heretofore known a type in which there are provided a switching element which is interposed in an electric power circuit for an electromagnetic valve interposed in a fuel passage and a combustion detecting element. The latter generates an electric change in response to such a change of a flame as caused by incomplete combustion or the like. The two elements are interconnected through a control circuit having a level detecting means which detects a predetermined level of the electric change of the combustion detecting element, so that by the predetermined level of the electric change of the combustion detecting element, the switching element may be opened to close the electromagnetic valve. It is usual with the detecting element of this apparatus that the same comprises an oxygen concentration cell element made of zirconia or the like which generates an electromotive force corresponding to an atmospheric oxygen concentration difference between electrodes provided on front and rear surfaces of an element body. It is also possible to use a variable resistance element made of titania or the like which generates a resistance change corresponding to an atmospheric oxygen concentration difference between the front and rear electrodes.
Either kind of those combustion detecting elements has such a defect that if the atmospheric oxygen concentration on the electrode brought in contact with a flame is changed by swaying of the flame caused by the wind or the like, it is so sensitive to the change thereof, that it generates almost the same electric change as in the case of incomplete combustion and thereby an unnecessary or unexpected closing of the electromagnetic valve results.